1. Field of the Invention
The present invention relates to a process for converting design data of repeated electronic circuits such as mask patterns of a LSI, and particularly to a process for converting mask data to arrays.
2. Description of the Related Art
In an integrated circuit (IC) or a large-scale integrated circuit (LSI), high density mounting of circuits is possible because of the regularity of circuit patterns, and large amount of design data is required accordingly. For this reason, it is a typical in an LSI, etc., because of the regularity of circuit patterns, that object data is compressed to a practical amount of data and then evaluations such as a logical simulation, a circuit simulation, or a design data check are performed.
For example, a process for manufacturing semi-conductor wafers includes a process for converting circuit patterns to CAM data for a photomask in order to create the photomask. In particular, since very large amount of data is handled for a LSI, a process called a “conversion-to-array process” is usually performed in this conversion process in order to decrease the amount of the mask data.
The conversion-to-array process is a process in which flat patterns arranged as mask patterns of a LSI are assumed as graphics, repeatability of the graphics is detected, and the graphics arranged in a lattice pattern are converted to array configuration data.
The array configuration is a configuration of data consisting of a master graphic, which is a reference graphic for arranging repeatedly, a repetition pitch in case that it is assumed that the master graphic is repeatedly arranged at positions in two dimensions, and the number of the repetitions.
In a conventional conversion-to-array process, array configuration data is created by selecting a master graphic, which is a reference graphic for repetition, from the graphics for mask patterns, and computing a repetition pitch which is the interval between the master graphic and a graphic just next to the master graphic, and the number of the repetitions, according to a procedure described, in detail, later.
In the conventional process, as a repetition pitch is the interval between a master graphic and a graphic congruent with and next to the master graphic for any arrangement of graphics, the computation of the repetition pitch is relatively simple, and the processing time of a computer may be kept in a practical range.
However, a useful result about the compression rate of data is not always obtained. In particular, in case that intervals between upper and lower graphics and between right and left graphics adjacent each other are not even, the number of arrays created is large, and thereby sufficient data compression may not be achieved.
It is therefore an object of the present invention to provide a method of efficiently converting-to-array and compressing data in a conversion-to-array process for mask patterns of a LSI.